In recent years, many researchers utilized infrared remote sensing technique to monitor the rock failure process under stress, and made numerous researches on the infrared radiation temperature characteristics in the rock failure process under stress. The research findings indicate the rock has a regular infrared radiation effect in the process from deformation to failure under stress, and there is an infrared anomaly omen before catastrophic failure of rock.
Since the beginning of 1990s, many experts and researchers have set up indoor thermal infrared observation and testing systems to make research on the relationship between rock deformation and temperature change, have accomplished many thermal infrared tests and experiments on the deformation of materials such as rock and coal, and the researches have received extensive attention. However, their observation results had high discreteness, and some of the observation results deviated from the traditional theory. For example, it is believed that the relationship between stress state and temperature change depends on the species of the rock. For example, some rocks exhibit a temperature rise characteristic when they are compressed, some rocks have no temperature change when they are compressed, and other rocks even exhibit a temperature drop characteristic when they are compressed; in addition, the amplitude of temperature change to the rock collapse point is different among different species of rocks. The main reason for such discreteness is that the tester didn't take appropriate measures to minimize the influences of environmental factors and background factors.
A part of the radiation received by a thermal infrared imager comes from the radiation of ambient and background reflection in the air path. The surface temperature of the tested object may change at any time, depending on the geographical location, season, solar radiation, sky radiation, climatic change, and air flow, and existence of any heat source, etc. at the test place. In addition, the surface of the tested object exchanges heat with the ambient medium uninterruptedly by radiation, convection, and conduction, etc. The ambient influences on the temperature of a tested object can be considered mainly in two aspects: environmental factors and background factors. The environmental factors mainly refer to the influences of the natural environment on the tested object, including direct solar radiation, sky radiation, earth background radiation and reflection of other radiations, air temperature change, wind speed, geographical latitude, and nearby landform and topography, etc. Under given geographical latitude, given orientation of the tested object, and given topographical conditions, the major influencing factors include solar radiation intensity, air temperature change, and wind speed, etc.